The present invention relates generally to a rotary duplicating machine, and more particularly to a rotary duplicating machine which is capable of printing individual lines of a printing form mounted on the printing roller of the machine.
Rotary printing rollers are already known, for instance from U.S. Pat. No. 2,967,477, in which the selection of particular lines or groups of lines of the printing form which are to be printed during a given rotation of the printing roller is carried out by means of cams which control the movement of the printing roller or the counter roller into or out of printing engagement with one another, and which in turn are controlled by electromagnets which move the cams into or out of a position in which they can control the movement of the respective roller. In these constructions the electromagnet must be very strong in order to obtain the proper movement of the respective cam. These relatively strong electromagnets are, however, to slow to provide for the necessary rapidity of the cam-shifting movement to thereby in turn effect relative shifting of the printing roller and the counter-pressure roller. This necessitates the utilization of relatively complicated and expensive secondary devices, such as impulse storage devices or the like.